Use of antibiotics and risk of breast cancer: a population-based case-control study

Association between Antibiotic Use and Subsequent Risk of Breast Cancer: A Nationwide Retrospective Cohort Study in South Korea

Several studies have revealed a possible association between antibiotic use and breast cancer in the Western population of women. However, its association with the Asian population remains unclear. Data utilized in this nationwide population-based retrospective cohort study were obtained from the Korean National Health Insurance Service database. The study population consisted of 4,097,812 women who were followed up from January 1, 2007, to December 31, 2019. Cox proportional hazards regression was utilized to calculate adjusted hazard ratio (aHR) and 95% confidence interval (CI) for the risk of breast cancer according to cumulative days of antibiotic use and the number of antibiotic classes used. It was discovered that women who used antibiotics for more than 365 days had a higher risk of breast cancer (aHR, 1.15; 95% CI, 1.09-1.21) in comparison with those who did not use antibiotics. In addition, an association was found among women who used five or more classes of antibiotics, showing a higher risk of breast cancer (aHR, 1.11; 95% CI, 1.05-1.17) compared with nonusers. Furthermore, compared with antibiotic nonusers, only users of cephalosporins (aHR, 1.09; 95% CI, 1.02-1.17) and lincosamides (aHR, 1.70; 95% CI, 1.20-2.42) had a higher risk of breast cancer. These findings support epidemiologic evidence that long-term use of antibiotics may be associated with a higher risk of breast cancer. This underscores the need for further studies to address the potential for residual confounding, confirm causation, and elucidate the underlying mechanisms. Prevention Relevance: This study found a probable duration-dependent association between antibiotic prescriptions and breast cancer risk. The findings indicate that long-term antibiotic use could be associated with an increased risk of breast cancer and highlight the need for further research to confirm causality and mechanisms.

Interactions between the tumor microbiota and breast cancer

Breast cancer is the most common malignancy in women worldwide. Changes in the microbiota and their metabolites affect the occurrence and development of breast cancer; however, the specific mechanisms are not clear. Gut microbes and their metabolites influence the development of breast cancer by regulating the tumor immune response, estrogen metabolism, chemotherapy, and immunotherapy effects. It was previously thought that there were no microorganisms in breast tissue, but it is now thought that there are microorganisms in breast cancer that can affect the outcome of the disease. This review builds on existing research to comprehensively analyze the role of gut and intratumoral microbiota and their metabolites in the development and metastasis of breast cancer. We also explore the potential function of the microbiota as biomarkers for prognosis and therapeutic response, highlighting the need for further research to clarify the causal relationship between the microbiota and breast cancer. We hope to provide new ideas and directions for the development of new methods for breast cancer treatment.

Novel insights at the crossroads of antibiotic use and cancer risk

The continuous use of antibiotics is associated with the spread of antimicrobial resistances and the not yet clear link to cancer development. Many conventional antibiotics have already shown different effects on a variety of cancer types raising questions for their rational use in cancer. However, discrepancy in the observed trend for some antibiotics reducing cancer development and being associated with higher risk of cancer underscores the lack of understanding the complex link between antibiotics and cancer. Here, we briefly summarize the possible antibiotic-mediated effects on cancer and conclude that those effects can be direct via i) specific targeting of tumor/cancer, ii) antimicrobial activity and iii) immunomodulatory activity whereby iv) indirectly caused effects primarily affect immune equilibrium between bacteria, cancer and immune cells. Furthermore, we also conclude that there is a great need for bulk profiling, comprehensive screening programs in all countries and in-depth studies to understand the risks and benefits of antibiotic use.

Macrolide antibiotics activate the integrated stress response and promote tumor proliferation

Macrolide antibiotics are widely used antibacterial agents that are associated with autophagy inhibition. This study aimed to investigate the association between macrolide antibiotics and malignant tumors, as well as the effect on autophagy, reactive oxygen species (ROS) accumulation and integrated stress response (ISR). The meta-analysis indicated a modestly higher risk of cancer in macrolide antibiotic ever-users compared to non-users. Further experiments showed that macrolides block autophagic flux by inhibiting lysosomal acidification. Additionally, azithromycin, a representative macrolide antibiotic, induced the accumulation of ROS, and stimulated the ISR and the activation of transcription factor EB (TFEB) and TFE3 in a ROS-dependent manner. Finally, animal experiments confirmed that azithromycin promoted tumor progression in vivo, which could be receded by N-acetylcysteine, an inhibitor of ROS and ISR. Overall, this study reveals the potential role of macrolide antibiotics in malignant progression and highlights the need for further investigation into their effects.

Antimicrobial drug use and the risk of glioma: A case-control study

BACKGROUND

The use of antibiotics has been associated with increased risks of various cancers. Comprehensive information on the association of antibiotic use with the risk of glioma is lacking.

METHODS

We performed a large case-control study based on the Clinical Practice Research Datalink (CPRD) GOLD from the United Kingdom. We identified 4423 glioma cases recorded between 1995 and 2020 and matched them to controls (1:10) on the date of diagnosis (i.e., the index date), age, sex, general practice, and number of years of medical history in the database prior to the index date. We conducted conditional logistic regression analyses to calculate odds ratios (ORs) with 95% confidence intervals (CIs). The exposures of interest were the use of antimicrobial drugs, including antibacterial, antiviral, antifungal, antiprotozoal, and anthelmintic drugs with specific subclasses, where possible.

RESULTS

We found no substantially increased risk of glioma after ever-use of antibiotics (OR 1.13, 95% CI 1.03-1.24). The risk did not increase with the increasing number of prescriptions received or with increasing time from first use to cancer diagnosis. The use of polyenes was associated with a weakly decreased risk of glioma (OR 0.81, 95% CI 0.67-0.96).

Analysis of Gut Microbiota in Patients with Breast Cancer and Benign Breast Lesions

Breast cancer (BC) and benign breast lesions (BBLs) are common diseases in women worldwide. The gut microbiota plays a vital role in regulating breast diseases' formation, progression, and therapy response. Hence, we explored the structure and function of gut microflora in patients with BC and BBLs. A cohort of 66 subjects was enrolled in the study. Twenty-six subjects had BC, 20 subjects had BBLs, and 20 matched healthy controls. High throughput 16S ribosomal RNA (16S rRNA) gene sequencing technology was used to determine the microbial community structure. Compared with healthy individuals, BC patients had significantly lower alpha diversity indices (Sobs index, p = 0.019; Chao1 index, p = 0.033). Sobs and Chao1 indices were also lower in patients with BBLs than healthy individuals, without statistical significance (p = 0.279, p = 0.314, respectively). Both unweighted and weighted UniFrac analysis showed that beta diversity differed significantly among the three groups (p = 3.376e-14, p < 0.001, respectively). Compared with healthy individuals, the levels of Porphyromonas and Peptoniphilus were higher in BC patients (p = 0.004, p = 0.007, respectively), whereas Escherichia and Lactobacillus were more enriched in the benign breast lesion group (p < 0.001, p = 0.011, respectively). Our study indicates that patients with BC and BBLs may undergo significant changes in intestinal microbiota. These findings can help elucidate the role of intestinal flora in BC and BBLs patients.

The involvement of oncobiosis and bacterial metabolite signaling in metastasis formation in breast cancer

Breast cancer, the most frequent cancer in women, is characterized by pathological changes to the microbiome of breast tissue, the tumor, the gut, and the urinary tract. Changes to the microbiome are determined by the stage, grade, origin (NST/lobular), and receptor status of the tumor. This year is the 50th anniversary of when Hill and colleagues first showed that changes to the gut microbiome can support breast cancer growth, namely that the oncobiome can reactivate excreted estrogens. The currently available human and murine data suggest that oncobiosis is not a cause of breast cancer, but can support its growth. Furthermore, preexisting dysbiosis and the predisposition to cancer are transplantable. The breast's and breast cancer's inherent microbiome and the gut microbiome promote breast cancer growth by reactivating estrogens, rearranging cancer cell metabolism, bringing about a more inflammatory microenvironment, and reducing the number of tumor-infiltrating lymphocytes. Furthermore, the gut microbiome can produce cytostatic metabolites, the production of which decreases or blunts breast cancer. The role of oncobiosis in the urinary tract is largely uncharted. Oncobiosis in breast cancer supports invasion, metastasis, and recurrence by supporting cellular movement, epithelial-to-mesenchymal transition, cancer stem cell function, and diapedesis. Finally, the oncobiome can modify the pharmacokinetics of chemotherapeutic drugs. The microbiome provides novel leverage on breast cancer that should be exploited for better management of the disease.

Comparison of the Gut Microbiota in Patients with Benign and Malignant Breast Tumors: A Pilot Study

The microbiome plays diverse roles in many diseases and can potentially contribute to cancer development. Breast cancer is the most commonly diagnosed cancer in women worldwide. Thus, we investigated whether the gut microbiota differs between patients with breast carcinoma and those with benign tumors. The DNA of the fecal microbiota community was detected by Illumina sequencing and the taxonomy of 16S rRNA genes. The α-diversity and β-diversity analyses were used to determine richness and evenness of the gut microbiota. Gene function prediction of the microbiota in patients with benign and malignant carcinoma was performed using PICRUSt. There was no significant difference in the α-diversity between patients with benign and malignant tumors (P = 3.15e-1 for the Chao index and P = 3.1e-1 for the ACE index). The microbiota composition was different between the 2 groups, although no statistical difference was observed in β-diversity. Of the 31 different genera compared between the 2 groups, level of only Citrobacter was significantly higher in the malignant tumor group than that in benign tumor group. The metabolic pathways of the gut microbiome in the malignant tumor group were significantly different from those in benign tumor group. Furthermore, the study establishes the distinct richness of the gut microbiome in patients with breast cancer with different clinicopathological factors, including ER, PR, Ki-67 level, Her2 status, and tumor grade. These findings suggest that the gut microbiome may be useful for the diagnosis and treatment of malignant breast carcinoma.

Role of Gut Microbiota Dysbiosis in Breast Cancer and Novel Approaches in Prevention, Diagnosis, and Treatment

Breast cancer is the most common cause of cancer-related deaths in women. Breast cancer is still a major cause of morbidity and mortality among women despite all the available diagnostic and treatment modalities. The gut microbiota has drawn keen interest as an additional environmental risk factor in breast cancer, especially in sporadic cases. This article explores factors that disrupt the normal gut microbial composition and the role of gut microbial dysbiosis in the development of breast cancer. We finalized 40 relevant articles after searching Pubmed and Google Scholar using regular keywords and the Medical Subject Headings (MeSH) strategy. Gut microbiota dysbiosis has been shown to play a role in the development of breast cancer via estrogen-dependent mechanisms and non-estrogen-dependent mechanisms involving the production of microbial-derived metabolites, immune regulation, and effects on DNA. The gut microbiota influence estrogen metabolism hence estrogen levels. The metabolites that have demonstrated anticancer properties include lithocholic acid, butyrate, and cadaverine. New approaches targeting the gut microbiota have come up and may yield new advances in the prevention, diagnosis, and treatment of breast cancer. They include the use of prebiotics, probiotics, and hormone supplements to restore normobiosis in the prevention and treatment of breast cancer.

Gut microbiome, body weight, and mammographic breast density in healthy postmenopausal women

PURPOSE

We examined gut microbiome (GM) profiles in relation to mammographic breast density (BD) and body mass index (BMI) in healthy postmenopausal women.

METHODS

Eligible women were postmenopausal, had a BMI ≤ 35 kg/m², and had not recently taken oral/IV antibiotics. All women provided a fecal sample and information on breast cancer risk factors. Mammographic BD was classified with the American College of Radiology's BI-RADS BD classification system. Bacterial DNA was isolated from fecal samples and the V1-V2 hypervariable regions of 16S rRNA were sequenced on the Illumina MiSeq platform. We examined associations of GM with indices of within-sample (alpha) diversity and the ratio of the two main phyla (Firmicutes and Bacteroidetes; F/B ratio) with BD and BMI.

RESULTS

Among 69 women with BD data, 39 had low BD (BI-RADS I/II) and 30 had high BD (BI-RADS III/IV). BMI was inversely associated with BD (mean BMI = 23.8 and 28.0 in women with high and low BD, respectively, p = 1.07 × 10^-5). Similar levels of GM diversity were found across weight groups according to Shannon (p = 0.83); Inverse Simpson (p = 0.97); and Chao1 (p = 0.31) indices. F/B ratio and microbiota diversity were suggestively greater in women with high vs. low BD (p = 0.35, 0.14, 0.15, and 0.17 for F/B ratio, Shannon, Inverse Simpson and Chao1, respectively).

CONCLUSION

Suggestive differences observed in women with high and low BD with respect to GM alpha diversity and prevalence of specific GM taxa need to be confirmed in larger studies.

Antibiotic use and the risk of breast cancer: A systematic review and dose-response meta-analysis

OBJECTIVE

Oral antibiotics are posed as a possible risk factor for breast cancer. Evidence is insufficient to determine whether the choice of antibiotic class could effect this potential association, and non-linearity has not been studied. We aimed to fill these important knowledge gaps.

METHODS

PubMed, Web of Science, Embase and a trial registry were searched from inception until January 2020, without any restrictions. Additionally, extensive manual searches were undertaken. Random-effects meta-analyses provided pooled risk estimates with 95 % confidence intervals (CI). Dose-response analyses modeling the relationship between number of antibiotic prescriptions and breast cancer risk were extended to non-linear models. Heterogeneity, publication bias and small-study effects were assessed.

RESULTS

Of 7805 identified publications ten were eligible, including 3,719,383 individuals and 84,485 breast cancer cases. The pooled breast cancer risk was modestly increased among individuals who ever used antibiotics (relative risk RR = 1.18, 95 %CI 1.08-1.29), also after excluding the last year prior diagnosis. This excess risk was seen among penicillin (RR = 1.09, 95 %CI 1.01-1.18), tetracycline (RR = 1.13, 95 %CI 1.04-1.24) and nitrofuran users (RR = 1.26, 95 %CI 1.05-1.52), whilst nitroimidazole and metronidazole use (RR = 1.05, 95 %CI 1.00-1.11) indicated for marginal association. No apparent association was found for other antibiotics. Data suggested for a non-linear dose-dependent relationship, with a seemingly protective effect after at least 35 prescriptions. However, these findings might partly be explained by limited power of dose-response analyses.

CONCLUSIONS

The association of antibiotics with breast cancer risk appears to differ between the various antibiotic classes. Whether this association is causal remains unclear, requiring further clarification and mechanistic studies.

Use of Antibiotics and Risk of Cancer: A Systematic Review and Meta-Analysis of Observational Studies

The association between antibiotic use and risk of cancer development is unclear, and clinical trials are lacking. We performed a systematic review and meta-analysis of observational studies to assess the association between antibiotic use and risk of cancer. PubMed, the Cochrane Library and EMBASE were searched from inception to 24 February 2019 for studies reporting antibiotic use and subsequent risk of cancer. We included observational studies of adult subjects with previous exposure to antibiotics and available information on incident cancer diagnoses. For each of the eligible studies, data were collected by three reviewers. Risk of cancer was pooled to provide an adjusted odds ratio (OR) with a 95% confidence interval (CI). The primary outcome was the risk of developing cancer in ever versus non-antibiotic users. Cancer risk’s association with antibiotic intake was evaluated among 7,947,270 participants (n = 25 studies). Overall, antibiotic use was an independent risk factor for cancer occurrence (OR 1.18, 95%CI 1.12–1.24, p < 0.001). The risk was especially increased for lung cancer (OR 1.29, 95%CI 1.03–1.61, p = 0.02), lymphomas (OR 1.31, 95%CI 1.13–1.51, p < 0.001), pancreatic cancer (OR 1.28, 95%CI 1.04–1.57, p = 0.019), renal cell carcinoma (OR 1.28, 95%CI 1.1–1.5, p = 0.001), and multiple myeloma (OR 1.36, 95%CI 1.18–1.56, p < 0.001). There is moderate evidence that excessive or prolonged use of antibiotics during a person’s life is associated with slight increased risk of various cancers. The message is potentially important for public health policies because minimizing improper antibiotic use within a program of antibiotic stewardship could also reduce cancer incidence.

Metagenomic Approaches for Understanding New Concepts in Microbial Science

Over the past thirty years, since the dawn of metagenomic studies, a completely new (micro) universe was revealed, with the potential to have profound impacts on many aspects of the society. Remarkably, the study of human microbiome provided a new perspective on a myriad of human traits previously regarded as solely (epi-) genetically encoded, such as disease susceptibility, immunological response, and social and nutritional behaviors. In this context, metagenomics has established a powerful framework for understanding the intricate connections between human societies and microbial communities, ultimately allowing for the optimization of both human health and productivity. Thus, we have shifted from the old concept of microbes as harmful organisms to a broader panorama, in which the signal of the relationship between humans and microbes is flexible and directly dependent on our own decisions and practices. In parallel, metagenomics has also been playing a major role in the prospection of "hidden" genetic features and the development of biotechnological applications, through the discovery of novel genes, enzymes, pathways, and bioactive molecules with completely new or improved biochemical functions. Therefore, this review highlights the major milestones over the last three decades of metagenomics, providing insights into both its potentialities and current challenges.

The Intestinal Microbiome and Estrogen Receptor-Positive Female Breast Cancer

The huge communities of residential microbes, including bacteria, viruses, Archaea, and Eukaryotes, that colonize humans are increasingly recognized as playing important roles in health and disease. A complex populous ecosystem, the human gastrointestinal (GI) tract harbors up to 10(11) bacterial cells per gram of luminal content, whose collective genome, the gut metagenome, contains a vastly greater number of individual genes than the human genome. In health, the function of the microbiome might be considered to be in dynamic equilibrium with the host, exerting both local and distant effects. However, 'disequilibrium' may contribute to the emergence of disease, including malignancy. In this review, we discuss how the intestinal bacterial microbiome and in particular how an 'estrobolome,' the aggregate of enteric bacterial genes capable of metabolizing estrogens, might affect women's risk of developing postmenopausal estrogen receptor-positive breast cancer. Estrobolome composition is impacted by factors that modulate its functional activity. Exploring variations in the composition and activities of the estrobolome in healthy individuals and in women with estrogen-driven breast cancer may lead to development of microbiome-based biomarkers and future targeted interventions to attenuate cancer risk.

Periodontal Disease and Breast Cancer: Prospective Cohort Study of Postmenopausal Women

BACKGROUND

Periodontal disease has been consistently associated with chronic disease; there are no large studies of breast cancer, although oral-associated microbes are present in breast tumors.

METHODS

In the Women's Health Initiative Observational Study, a prospective cohort of postmenopausal women, 73,737 women without previous breast cancer were followed. Incident, primary, invasive breast tumors were verified by physician adjudication. Periodontal disease was by self-report. HRs and 95% confidence intervals (CI) were estimated by Cox proportional hazards, adjusted for breast cancer risk factors. Because the oral microbiome of those with periodontal disease differs with smoking status, we examined associations stratified by smoking.

RESULTS

2,124 incident, invasive breast cancer cases were identified after mean follow-up of 6.7 years. Periodontal disease, reported by 26.1% of women, was associated with increased breast cancer risk (HR 1.14; 95% CI, 1.03-1.26), particularly among former smokers who quit within 20 years (HR 1.36; 95% CI, 1.05-1.77). Among current smokers, the trend was similar (HR 1.32; 95% CI, 0.83-2.11); there were few cases (n = 74) and the CI included the null. The population attributable fraction was 12.06% (95% CI, 1.12-21.79) and 10.90% (95% CI, 10.31-28.94) for periodontal disease among former smokers quitting within 20 years and current smokers, respectively.

CONCLUSION

Periodontal disease, a common chronic inflammatory disorder, was associated with increased risk of postmenopausal breast cancer, particularly among former smokers who quit in the past 20 years.

IMPACT

Understanding a possible role of the oral microbiome in breast carcinogenesis could impact prevention.

Frequent antibiotic use and second breast cancer events

BACKGROUND

Antibiotic use may be associated with higher breast cancer risk and breast cancer mortality, but no study has evaluated the relation between antibiotic use and second breast cancer events (SBCE).

METHODS

We conducted a retrospective cohort study among women ≥18 years, diagnosed with incident stage I/II breast cancer during 1990-2008. Antibiotic use and covariates were obtained from health plan administrative databases and medical record review. Frequent antibiotic use was defined as ≥4 antibiotic dispensings in any moving 12-month period after diagnosis. Our outcome was SBCE defined as recurrence or second primary breast cancer. We used multivariable Cox proportional hazards models to estimate HR and 95% confidence intervals (CI), accounting for competing risks.

RESULTS

A total of 4,216 women were followed for a median of 6.7 years. Forty percent were frequent antibiotic users and 558 (13%) had an SBCE. Results are suggestive of a modest increased risk of SBCE (HR, 1.15; 95% CI, 0.88-1.50) among frequent antibiotic users compared with nonusers. Any potential increased risk was not supported when we evaluated recent use and past use. We observed no dose-response trends for SBCE with increasing duration of antibiotic use nor did we find evidence for altered SBCE risk in the antibiotic classes studied.

CONCLUSIONS

Frequent antibiotic use may be associated with modestly elevated risk of SBCEs, but the association was not significant.

IMPACT

Additional investigation by antibiotic class and underlying indication are important next steps given the high prevalence of frequent antibiotic use and growing number of breast cancer survivors.

Endocarditis and risk of cancer: a Danish nationwide cohort study

BACKGROUND

Endocarditis may be a marker for bacteremia-associated occult cancer. Intensive antibiotic treatment in endocarditis is suggested to reduce long-term cancer risk. We examined these hypotheses in a nationwide cohort study.

METHODS

Endocarditis patients and cancer cases were identified from the Danish National Registry of Patients and the Danish Cancer Registry during 1978-2008. We compared the incidences of various cancers among study subjects to expected incidences based on national age-, sex-, and site-specific rates.

RESULTS

We observed 997 cancers among 8445 endocarditis patients (median follow-up of 3.5 years), reflecting an increased standardized incidence rate (SIR) of 1.61 (95% confidence interval [CI], 1.51-1.71). Cancer risk was highly elevated during the first 3 months of follow-up (SIR=8.03; 95% CI, 6.92-9.26), partly due to a 15- to 30-fold increased risk of hematological or liver cancers. Between 3-month and 5-year follow-ups, cancer incidence remained 1.5-fold higher than expected, including 2- and 4-fold increased SIRs for colorectal and liver cancers, respectively. Beyond 5 years of observation, the overall cancer SIR was 1.21 (95% CI, 1.10-1.34). Long-term associations were weak for several cancers hypothesized to be associated with antibiotic use, including prostate, gastric, and breast cancer.

CONCLUSION

Endocarditis is a substantial clinical marker for presence of occult cancer. We found no evidence of decreased long-term cancer risk after antibiotic treatment for endocarditis.

Antibiotic use and risk of gynecological cancer

OBJECTIVES

Several studies addressed the association between antibiotic use and breast cancer risk. The objective of this study was to assess the association between antibiotic use and risk of cervical, ovarian, and uterine cancer.

STUDY DESIGN

We carried out a population-based case-control study using data from Saskatchewan Health administrative databases (Canada) between the years 1981 and 2000. Cases were matched to 4 controls, using incidence density sampling. The effect of dosage and timing of antibiotic use, over a minimum of 15 years before diagnosis, on cervical, ovarian, or uterine cancer risk was assessed. Number of prescriptions and number of pills were used as exposure definitions. The effect of different classes of antibiotics on cancer risk was also studied.

RESULTS

A total of 1225 cancer cases [192 cervical, 445 ovarian, and 588 uterine] and 4900 matched controls were included in this study. Antibiotic exposure (number of prescriptions) during the period of 1-15 years in the past was significantly associated with a reduced risk of cervical cancer; Relative Risk (RR)=0.40, 0.31, 0.26, and 0.29 for the four exposure quartiles, respectively. No association was found for ovarian or uterine cancer. When number of pills was considered, similar results were found. There was no effect of the timing or class of antibiotic exposure on cervical cancer risk.

CONCLUSIONS

Antibiotic exposure up to 15 years in the past was associated with a decreased risk of cervical cancer. The lack of temporal trends and the absence of class specific effects suggest a non-causal relationship.

Can rye intake decrease risk of human breast cancer?

BACKGROUND

Rye contains more fibre and bioactive compounds than other cereals used for bread production. The fibre and compounds of the fibre complex could provide protection against breast cancer (BC).

OBJECTIVE

To review the evidence and theoretical background for a role of rye and some of its components in the prevention of BC.

DESIGN

A short review based to a great extent on the work by scientists in the Nordic countries.

RESULTS

Some of the possible mechanisms by which the fibre complex could reduce BC risk are presented. The fibre through its effect on fermentation increases esterification of bile acids reducing toxicity of the free bile acids and is involved in the production of butyrate with potential anticancer effects including BC. The fibre reduces the enterohepatic circulation of the oestrogens leading to lower plasma oestrogen concentrations. The fibre complex contains bioactive compounds such as lignans and alkylresorcinols that are antioxidative and potentially anticarcinogenic. In addition, vitamins, minerals, and phytic acid in rye may provide protection against BC.

CONCLUSION

Rye products made from wholegrain rye flour are likely to contribute to reduced BC risk.

Incidence and risk of chondrolysis in Denmark: A nationwide population-based study

BACKGROUND

Chondrolysis is a rare disease with destruction of cartilage of joints. Incidence and risk factors have not been studied in a formal epidemiologic population-based setting.

METHODS

We used the Danish National Registry of Patients (NRP) covering all Danish hospitals to identify all cases of chondrolysis from 1994 to 2008. Incidence rates were estimated using the general population as the denominator. For each chondrolysis patient, 10 age-matched population controls were sampled for a case-control analysis. For cases and controls, we ascertained in the NRP history of diabetes, rheumatoid arthritis, orthopedic surgery, including surgery of shoulder and upper arm, injury to shoulder girdle or upper arm, and treatment with pain pump. We determined the prevalence of these risk factors in cases and controls, and computed odds ratios (OR).

RESULTS

We identified 43 patients with chondrolysis in the 15-year study period. The incidence rate was 5.5 per 10,000,000 person-years. Diabetes was more prevalent in chondrolysis cases, compared with the 430 controls (OR = 6.7; 95% confidence intervals [CI]: 1.1-39.9). Orthopedic surgery was also associated with an increased risk of chondrolysis (OR = 28.8, 95% CI: 11.0-75.6), while previous injury was not (OR = 0.8; 95% CI: 0.1-5.9).

CONCLUSION

Chondrolysis was rarely diagnosed in Denmark. Diabetes and orthopedic surgery may be risk factors.

Association between antibiotic use and risk of prostate cancer

The association between antibiotics and risk of cancer has been addressed in different studies, most of which were addressing breast cancer. The objective of this study was to assess the association between antibiotics use and risk of prostate cancer. We carried out a population-based case-control study using data from Saskatchewan Health administrative databases (Canada) between the years 1981 and 2000. Cases identified by the Saskatchewan Cancer Agency were matched to 4 controls, using incidence density sampling. The effect of dosage and timing of antibiotic use, over a minimum of 15 years before diagnosis, on prostate cancer risk was assessed. Number of prescriptions and number of tablets were used as exposure definitions. Moreover, the effect of different classes of antibiotics on prostate cancer was also studied. A total of 4,052 prostate cancer cases and 16,208 matched controls were included in this study. Antibiotics exposure (number of prescriptions) during the period of 1-15 years in the past was significantly associated with an increased risk of prostate cancer; RR = 1.69, 2.61, 2.71, and 2.83 for the 4 quartiles, respectively, p-trend = 0.0001. When number of units was taken as the exposure definition, similar results were found. We did not find any effect of the timing or class of antibiotic exposure on prostate cancer risk. We found a dose-dependent association between antibiotics exposure up to 15 years in the past and risk of prostate cancer. However, the lack of temporal trends and the absence of class specific effects suggest a noncausal relationship.

Use of selective serotonin reuptake inhibitors and risk of re-operation due to post-surgical bleeding in breast cancer patients: a Danish population-based cohort study

Background

Selective serotonin reuptake inhibitors (SSRI) decrease platelet-function, which suggests that SSRI use may increase the risk of post-surgical bleeding. Few studies have investigated this potential association.

Methods

We conducted a population-based study of the risk of re-operation due to post-surgical bleeding within two weeks of primary surgery among Danish women with primary breast cancer. Patients were categorised according to their use of SSRI: never users, current users (SSRI prescription within 30 days of initial breast cancer surgery), and former users (SSRI prescription more than 30 days before initial breast cancer surgery). We calculated the risk of re-operation due to post-surgical bleeding within 14 days of initial surgery, and the relative risk (RR) of re-operation comparing SSRI users with never users of SSRI adjusting for potential confounders.

Results

389 of 14,464 women (2.7%) were re-operated. 1592 (11%) had a history of SSRI use. Risk of re-operation was 2.6% among never users, 7.0% among current SSRI users, and 2.7% among former users. Current users thus had an increased risk of re-operation due to post-operative bleeding (adjusted relative risk = 2.3; 95% confidence interval (CI) = 1.4, 3.9) compared with never users. There was no increased risk of re-operation associated with former use of SSRI (RR = 0.93, 95% CI = 0.66, 1.3).

Conclusions

Current use of SSRI is associated with an increased risk of re-operation due to bleeding after surgery for breast cancer.

Cox-2 expression in ovarian malignancies: a review of the clinical aspects

COX-2 is an inducible enzyme expressed only in response to stimuli such as mitogens, cytokines, growth factors or hormones, and is pro-inflammatory. It plays an important role in tumorigenesis. The purpose of the present report is to review the clinical aspects of COX-2 expression in ovarian malignancies. A PubMed (http://www.pubmed.gov/) search of investigations published from July 2001 until August 2008 and containing the term COX-2 in combination with ovarian malignancies was conducted. The clinical aspects of the relevant investigations were reviewed. COX-2 is expressed in ovarian tumors of low malignant potential (LMP), in epithelial ovarian carcinoma (EOC) and primary peritoneal carcinoma (PPC) and apparently plays a role in their carcinogenesis. Its expression seems to be correlated with VEGF that serves as a predictor of poor prognosis in some non-gynecologic malignancies. COX-2 expression is higher in EOC than in LMPs. The results with regard to the association between COX-2 expression and prognostic factors, response to treatment and outcome in ovarian malignancies are inconsistent. Clinical studies dealing with the effect of COX-2 inhibitors on outcome are scarce. The use of COX-2 expression in gynecological malignancies in clinical practice remains to be elucidated.

Digoxin treatment is associated with an increased incidence of breast cancer: a population-based case-control study

INTRODUCTION

Laboratory and epidemiologic studies have suggested a modifying effect of cardiac glycosides (for example, digoxin and digitoxin) on cancer risk. We explored the association between digoxin treatment and invasive breast cancer incidence among postmenopausal Danish women.

METHODS

We used Danish registries to identify 5,565 postmenopausal women diagnosed with incident invasive breast carcinoma between 1 January 1991 and 31 December 2007, and 55,650 matched population controls. Cardiac glycoside prescriptions were ascertained from county prescription registries. All subjects had at least 2 years of recorded prescription drug and medical history data. We estimated the odds ratio associating digoxin use with breast cancer in conditional logistic regression models adjusted for age, county of residence, and use of anticoagulants, non-steroidal anti-inflammatory drugs (NSAIDs), aspirin, and hormone replacement therapy. We also explored the impact of confounding by indication and detection bias.

RESULTS

Digoxin was the sole cardiac glycoside prescribed to subjects during the study period. There were 324 breast cancer cases (5.8%) and 2,546 controls (4.6%) with a history of digoxin use at least 1 year before their index date (adjusted odds ratio (OR): 1.30; 95% confidence interval: 1.14 to 1.48). The breast cancer OR increased modestly with increasing duration of digoxin exposure (adjusted OR for 7 to 18 years of digoxin use: 1.39; 95% confidence interval: 1.10 to 1.74). The association was robust to adjustment for age, receipt of hormone replacement therapy, coprescribed drugs, and confounding by indication. A comparison of screening mammography rates between cases and controls showed no evidence of detection bias.

CONCLUSIONS

Our results suggest that digoxin treatment increases the risk of invasive breast cancer among postmenopausal women.

Antibiotic use predicts an increased risk of cancer

Antibiotic use has been hypothesized to be associated with the risk of cancer but the evidence is sparse and inconsistent. The aim of the present study was to determine whether antibiotic use predicts the development of various cancers. This nationwide cohort study included 3,112,624 individuals, aged 30-79 years, with no history of cancer. Information on their antibiotic use between 1995 and 1997 was obtained from the Drug Prescription Registry. During the period 1998-2004, 134,070 cancer cases were ascertained from the Finnish Cancer Registry. Cox proportional hazards regression was used to estimate the relative risks (RRs) with 95% confidence intervals (95% CIs). Antibiotic use was associated with an increased risk of cancer: for categories of increasing antibiotic use (0-1, 2-5 and >/=6 prescriptions), RRs (95% CIs) for cancer were 1.0 (reference), 1.27 (1.26-1.29) and 1.37 (1.34-1.40). RRs (for comparison of lowest and highest exposure group) for the most common primary sites i.e. prostate, breast, lung and colon were 1.39 (1.31-1.48), 1.14 (1.09-1.20), 1.79 (1.67-1.92), and 1.15 (1.04-1.26), respectively. RRs for other primary sites varied between 0.90 (0.76-1.05) for ovary to 2.60 (1.60-4.20) for endocrine gland (excluding thyroid). In conclusion, antibiotic use predicts an increased risk of cancer. Because of the design of our study the possibility of residual confounding cannot be excluded and further studies are required to confirm the results.

Antibiotic use and the risk of lung cancer

Antibiotic use has been associated with an increased risk of cancer in epidemiologic studies. We evaluated the association between antibiotic use and the risk of primary lung cancer by conducting a prospective case-control study nested in a cohort of subjects who were 40 to 84 years old in 1995 to 2004, with at least 2 years of enrollment in The Health Improvement Network. There were 4,336 cases of primary lung cancer. A random sample of 10,000 controls was frequency matched to the cases for age, sex, and calendar year of diagnosis. Antibiotic exposure was measured by the total number of antibiotic prescriptions and the cumulative number of days on antibiotics since enrollment. We discounted exposure 1 year before the date of cancer diagnosis. Relative risks (RR) and 95% confidence intervals (95% CI) were estimated using conditional logistic regression. Smoking, chronic obstructive pulmonary disease, respiratory infections, body mass index, and health care utilization were introduced in the model. Compared with subjects with no prescription of antibiotics before the index date, the crude RR of lung cancer was 2.52 (95% CI, 2.25-2.83) among those who received 10 or more prescriptions. The corresponding RR was 1.31 (95% CI, 1.10-1.57) upon adjustment for confounders. We used directed acyclic graphs to illustrate that the observed higher risk of lung cancer among antibiotic users may be due to the increased frequency of infections in patients with subclinical cancer and to shared causes between cancer and infections. Current evidence is insufficient to support or refute a carcinogenic effect of antibiotics.

Risk of breast cancer in relation to antibiotic use

BACKGROUND

There are conflicting results in the literature regarding the association between the antibiotic exposure and breast cancer risk. The aim of this study was to assess this association using a population-based approach.

METHODS

The source population was the dynamic cohort defined by membership in the Saskatchewan Prescription Drug Plan (Canada) between the years 1981 and 2000. Four matched controls were selected for each case identified by the Saskatchewan Cancer Agency, using incidence density sampling. Detailed drug exposure over a minimum of 15 years before diagnosis allowed studying the respective effects of dosage and timing of antibiotic use on breast cancer risk. Two antibiotic exposure definitions were used: the number of prescriptions and the number of units (tablets, capsules, etc.), which were further categorized into quartiles.

RESULTS

A total of 3099 breast cancer cases and 12,396 matched controls were included. The incidence of breast cancer was higher in subjects who had more antibiotic prescriptions during the 1-15 years prior to the index date (RRs = 1.50, 1.63, 1.71 and 1.79 for the four quartiles, respectively, p-trend = 0.0001). Similar results were found when a number of units were considered. We did not find any effect of the timing of antibiotic exposure on breast cancer risk. Similar patterns of increased risk of breast cancer were detected for the specific antibiotic classes.

CONCLUSIONS

We observed a dose-dependent increase in breast cancer risk in association with the antibiotic exposure up to 15 years in the past. However, the lack of temporal trends and the absence of class-specific effects suggest a non-causal relationship.

Lignans and human health

This review focuses on the possible role in human health of the consumption of lignan-rich foods. Most of the plant lignans in human foods are converted by the intestinal microflora in the upper part of the large bowel to enterolactone and enterodiol, called mammalian or enterolignans. The protective role of these compounds, particularly in chronic Western diseases, is discussed. Evidence suggests that fiber- and lignan-rich whole-grain cereals, beans, berries, nuts, and various seeds are the main protective foods. Many factors, in addition to diet, such as intestinal microflora, smoking, antibiotics, and obesity affect circulating lignan levels in the body. Lignan-rich diets may be beneficial, particularly if consumed for life. Experimental evidence in animals has shown clear anticarcinogenic effects of flaxseed or pure lignans in many types of cancer. Many epidemiological results are controversial, partly because the determinants of plasma enterolactone are very different in different countries. The source of the lignans seems to play a role because other factors in the food obviously participate in the protective effects. The results are promising, but much work is still needed in this area of medicine.

Antibiotics and risk of breast cancer: up to 9 years of follow-up of 2.1 million women

Antibiotic use has been associated with risk of breast cancer in previous reports. Using Cox proportional hazards analysis, we evaluated this association in 2,130,829 adult female subscribers of a health care program according to their receipt of prescriptions of antibiotics from outpatient pharmacies. Hormone use was taken into account. Altogether, 18,521 women developed breast cancer in up to 9.4 years of follow-up. Use of any antibiotic was associated with slightly increased risk [hazard ratio (HR), 1.14; 95% confidence interval (95% CI), 1.10-1.18] but there was little, if any, evidence of dose response, with HR of 1.17 (95% CI, 0.97-1.42) for >1,000 days of use compared with no use. The only two weakly associated antibiotic groups (HR >1.10 for >100 days of use) were tetracyclines and macrolides with HRs (95% CI) of 1.23 (1.11-1.36) and 1.16 (0.98-1.36), respectively. An association of lincosamides with breast cancer in an earlier, smaller database was not confirmed, but follow-up was too short in the present data for adequate evaluation. Medical record review suggested that acne and/or rosacea could be the underlying factor, associated with long-term antibiotic therapy and found by others to be associated with risk of breast cancer. Although causality cannot be ruled out, the observed associations of antibiotics overall, tetracyclines, and macrolides with breast cancer were weak and could be explained by uncontrolled confounding by the diseases being treated or by other factors.

Influence of Antibiotic Treatment on Breast Carcinoma Development in Proto-neuTransgenic Mice

The effect of prolonged antibiotic treatments on tumor development was evaluated in proto-neu transgenic mice, which spontaneously develop mammary carcinomas. Virgin transgenic mice were treated with metronidazole/ciprofloxacin or gentamicin through the drinking water. The hazard ratio [HR; 95% confidence interval (95% CI)] of breast cancer occurrence in metronidazole/ciprofloxacin-treated mice was more than triple that for controls [3.11 (1.13-8.53); P = 0.028], whereas only a slight increase in HR (95% CI) was observed in gentamicin-treated mice [1.39 (0.56-3.47); P = 0.481]. Tumor growth rate in gentamicin-treated mice was significantly faster than in untreated control mice (P = 0.043). Moreover, mammary glands from mice treated with either antibiotic regimen showed increased lobulization, with more numerous and more developed terminal ductal lobular units than in controls. These results indicate that prolonged exposure to relevant doses of antibiotics affects the mammary glands in this particular model of HER-2/neu transgenic mice; further studies to understand the precise mechanism by which antibiotic treatments influence mammary gland differentiation are critical.

Association between Antibiotic use Prior to Breast Cancer Diagnosis and Breast Tumour Characteristics (United States)

OBJECTIVE

To determine if breast tumour characteristics varied by antibiotic use prior to diagnosis in 2,266 women with primary, invasive breast cancer.

METHODS

Subjects were women enrolled at Group Health Cooperative, a health plan in western Washington state, for at least 1 year and diagnosed with breast cancer between 1 January 1993 and 30 June 2001. Case status, tumour features, and patient characteristics were ascertained from the Surveillance, Epidemiology, and End Results cancer registry and Group Health Cooperative electronic files. Prescription information was obtained from electronic pharmacy records.

RESULTS

Compared to non-use, antibiotic use prior to breast cancer diagnosis was not associated with a less favourable tumour profile (as measured by cancer stage, grade, and size), oestrogen receptor negative tumours, or lobular histology, after controlling for age and length of enrollment. Nonetheless, while not achieving statistical significance, our results suggest that antibiotic use may be associated with less favourable breast tumour features.

CONCLUSIONS

Overall, we found no association between antibiotic use and breast tumour features and no dose-response gradient. However, the results are consistent with the possibility that antibiotic use may increase the risk of less favourable tumours. Larger studies are required to further investigate this hypothesis.